1. Field of the Invention
The present invention relates to beacon assemblies. More specifically, the present invention relates to beacon assemblies used to provide optical and thermal guidance for aerodynamic vehicles.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Tube launched optically tracked wire guided missile systems generally include a launcher and a wire guided missile. The launcher is equipped with a gunners optical sight and an electronic guidance computer which automatically sends steering commands to the missile in flight over the wire or optical command link. A light source in the tail of the missile is activated after launch or immediately prior thereto. The light source is detected by a sensor in the launcher. The sensor is boresighted with the gunner's telescope and allows the launcher to track the missile along its flight path. The sensor and associated processing circuitry measures the angle between the missile and the gunner's line-of-sight. These displacements are transformed by the computer into guidance commands which are sent to the missile. The gunner need only keep the crosshairs of the telescope on the target during missile flight.
Unfortunately, in a hostile environment, the ability of the launcher to track the light source (and hence the missile) may be impaired by natural and artificial impediments and countermeasures including fog haze and smoke. When augmented by a forward looking infrared (FLIR) sensor and display, the operator has the capability of seeing and hitting many targets which would otherwise be obscured. For this purpose, the system is augmented with a thermal beacon which is activated prior to launch. If the system is unable to track the visible (typically xenon) light source, handoff to the thermal source occurs.
To guard against certain countermeasures intended to confuse the launcher, a system was developed to blink the thermal beacon on command from the launcher and thereby distinguish from a countermeasure source. U.S. Pat. No. 4,595,258, issued June 17, 1986 to G. W. LeCompte discloses one such arrangement. This patent, entitled Shutter for Radiation Source of Extended Area, provides a shutter for producing a pulsed output from a thermal beacon or other radiant source. The shutter includes an optical plate and a shutter plate mounted on the radiant face of the thermal source. The referenced patent discloses a particularly advantageous design by which the plates are perforated so that when the plates are rotated relative to each other, the holes are aligned in one position to allow thermal energy or light from the beacon to pass. In a second position, the holes in the two plates are out of alignment and the radiant energy therefrom is blocked.
While the LeCompte design has been found to be particularly well suited for tube launched optically tracked wire guided missiles designed to accommodate a shuttered beacon, a need remains in the art for an arrangement which would permit missiles in the field to be retrofit with a thermal beacon.